Emily Viau
Grand Canyon University, USA
Title: Measuring Bioenergy Potential of City Food, Grease, Grass, and Zoo Manure Mixes.
Biography
Biography: Emily Viau
Abstract
Food recycling is the next frontier for cities looking to reduce costs for solid waste, to create clean energy, and to make good soil in parks – how? With anaerobic digestion (AD), a technology already used for wastewater, but only recently being applied to food and grease destined for a landfill. Anaerobic digestion is used throughout Europe for decades for creating biogas electricity or CNG fuel and US cities are now looking to apply this technology. The City of Tempe, a univeristy town in Arizona, set out to develop a good city recipe for making biogas with food, grease, manure, and grass wastes that were not currently recycled at its local businesses. In a public-private collaboration with Fresh Recycling Inc, and the Global Sustianability Solutions Services, a program of the Walton Sustainability Solutions Initiatives at Arizona State University, and the ASU Biodesign Institute, the city performed a first phase feasibilitiy study used a bench-scale biomethane potential (BMP) assay optimized for city labs to test food and grease for energy potential. Understanding a good recipe for a City anaerobic digester means balancing high energy feedstocks, like grease and food, with buffering feeds, like grass and manure, to keep microorganisms functioning and not foaming. Bench-scale digesters were then used to show the methane potential of food and grease samples from schools, major food manufacturers, restaurants and a golf course. The experiments measured methane and total gas production for 40-45 days for each feed at a low feeding rate, while monitoring for toxicity to microbes. Next, this information was used to develop two City food and grease ‘recipes’ that would limit toxicity caused by certain feedstocks; we created a ‘City Regular’ mix and a ‘City Industrial’ recipe and then combined these mixes with eight different animal manures, from elephant to rhino to sheep to horse. The first phase BMP studies will be presented here. Grass was the most productive long-term gas producer alone. Food – grease recipes with manure and grass were the best for gas production within a balanced system. Bench-scale digestion studies provide a nice jumping point for Cities to recycle food on a large scale from city restaurants and food producers. Tempe has optimized this biogas experimental method for future experiments, as food and grease feeds change and for collaboration with other cities.